Curable coating composition

ABSTRACT

Curable coating compositions which contain, as the binder, one or more olefinically unsaturated compounds containing urethane groups, with or without one or more olefinically unsaturated compounds copolymerizable therewith, in which the olefinically unsaturated compound containing urethane groups is a reaction product of vinyl isocyanate and a compound which contains at least one hydroxyl group and at least one radical of an ester of an α,β-olefinically unsaturated carboxylic acid of 3 to 6 carbon atoms. The compositions may, for example, be used for the manufacture of coatings which can be cured with electron beams.

This is a continuation, of application Ser. No. 821,550 filed Aug. 3,1977 now abandoned.

The present invention relates to a curable coating composition whichcontains, as the component forming the binder, a vinylurethane which hasbeen obtained by reacting vinyl isocyanate with a compound whichcontains at least one free hydroxyl group and at least one radical of anester of an α,β-olefinically unsaturated carboxylic acid of 3 to 6carbon atoms.

Coating compositions comprising solutions of high molecular weight orlow molecular weight unsaturated compounds in vinyl monomers have beendisclosed. If vinyl compounds which copolymerize rapidly, e.g. acryliccompounds, are used, such systems can be cured with high energyradiation. However, acrylic compounds have the disadvantage that theyare, in general, toxic and cause severe irritation of the skin.

A process has also already been disclosed, in German Laid-OpenApplication DOS No. 20 64 701.2-43, for the manufacture of coatings bycuring olefinically unsaturated polymeric materials containing urethanegroups, these materials, with or without admixture of olefinicallyunsaturated monomeric compounds, being cured by means of ionizing rays;the olefinically unsaturated polymeric material containing urethanegroups comprises at least two ##STR1## units and has been obtained byreacting hydroxylic oligomers or polymers of molecular weight from 500to 10,000 with vinyl isocyanate. However, these products still requireimprovement in respect of reactivity and hardness.

It is an object of the present invention to provide coating compositionswhich represent further improvements in respect of these properties andin addition have the advantage that they can also be cured by means ofultraviolet radiation and peroxides and that they adhere well to ametallic substrate.

We have found, surprisingly, that this object can be achieved in anadvantageous manner by providing the coating compositions according tothe present invention.

The present invention relates to a curable coating composition whichcontains, as the component forming the binder, one or more olefinicallyunsaturated compounds (A) containing urethane groups, with or withoutone or more other olefinically unsaturated compounds (B) which arecopolymerizable with (A) but differ from (A), in which the olefinicallyunsaturated compound (A) which contains urethane groups is a reactionproduct of vinyl isocyanate and a compound which contains at least onehydroxyl group and at least one radical of an ester of anα,β-olefinically unsaturated carboxylic acid of 3 to 6 carbon atoms.

Component (A) may be a reaction product of an ester, containing at leastone free hydroxyl group, of an α,β-olefinically unsaturated carboxylicacid of 3 to 6 carbon atoms with vinyl isocyanate or may be a compoundof the general formula ##STR2## where x and y may be identical ordifferent and each is a number from 1 to 5, R is hydrogen or methyl, R'is a divalent linear or branched radical of 2 to 16 carbon atoms whichmay or may not contain oxa groups, or is a divalent cycloaliphaticradical of 5 to 12 carbon atoms, R" is a divalent linear or branchedaliphatic, cycloaliphatic or aromatic radical of 6 to 15 carbon atomsand R" is a radical which is derived from a polyhydric alcohol, apolyether-ol or a polyester-ol and which has a valency corresponding tothe sum of x+y.

The curable coating compositions of the invention have very advantageousprocessing properties and are in particular distinguished by their lowviscosity and high reactivity.

The following details are to be noted with respect to the componentsfrom which the curable coating compositions of the invention aresynthesized:

(A) Suitable esters of α,β-olefinically unsaturated carboxylic acids of3 to 6 carbon atoms, which esters contain one or more free hydroxylgroups and may be used to synthesize the vinylurethanes (A), are theesters of α,β-olefinically unsaturated monocarboxylic acids, e.g.acrylic acid, methacrylic acid or α-cyanoacrylic acid, with dihydric orpolyhydric alcohols, e.g. linear, branched or cycloaliphatic diols oroxa-alkanediols of up to 12 carbon atoms, e.g. ethylene glycol, 1,2- and1,3-propylene glycol, butane-1,4-diol, butane-1,3-diol andbutane-1,2-diol, pentanediol, hexanediol, diethylene glycol, triethyleneglycol, dipropylene glycol, dibutylene glycol and cyclohexanediol,triols, e.g. glycerol, trimethylolpropane and tris-(hydroxyethyl)isocyanurate, and alcohols of higher functionality, e.g.pentaerythritol, dipentaerythritol, sorbitol and mannitol; these estersmust retain at least one free hydroxyl group. Preferred suitablehydroxylic esters are, for example, alkylene glycol monoacrylates, e.gethylene glycol monoacrylate, propanediol monoacrylate and butanediolmonoacrylate, and epoxide-acrylates obtained from glycidyl ethers ofmonohydric or polyhydric alcohols or phenols or from glycidyl esters ofaliphatic, cycloaliphatic and aromatic monocarboxylic and polycarboxylicacids and from mono- or poly-epoxidized cycloaliphatic hydrocarbons. Thereaction of these hydroxylic esters with vinyl isocyanate is carried outin the conventional manner, preferably in the presence of tin compoundsas the catalyst and/or in the presence of inert solvents, and in generalabout equivalent amounts of isocyanate groups are reacted with the freehydroxyl groups of the hydroxylic ester. If, however, hydroxylic esterswith more than one free hydroxyl group are reacted with vinylisocyanate, it suffices in each case to react 1 mole of vinyl isocyanatewith 1 mole of the hydroxylic ester. Vinylurethanes obtained fromhydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl acrylate andlow-viscosity epoxide acrylates, e.g. the adduct of 2 moles of acrylicacid with 1 mole of butanediol diglycidyl ether, are preferred.

The olefinically unsaturated compound (A), containing urethane groups,of the general formula ##STR3## where x and y are identical or differentand each is a number from 1 to 5, preferably from 1 to 3, R is hydrogenor methyl, R' is a divalent linear or branched radical of 2 to 16,preferably of 2 to 4, carbon atoms or a divalent cycloaliphatic radicalof 5 to 12, preferably of 5 to 8, carbon atoms, R" is a divalent linearor branched aliphatic, cycloaliphatic or aromatic radical of 6 to 15carbon atoms and R'" is a radical derived from a polyhydric alcohol,polyether-ol or polyester-ol and having a valency corresponding to thesum of x+y, are in general manufactured by first reacting a hydroxyalkylacrylate or hydroxyalkyl methacrylate, e.g. the acrylic acid ormethacrylic acid monoester of a linear or branched dihydric alcohol of 2to 16 carbon atoms which may or may not contain oxa groups, e.g.ethylene glycol, propane-1,2-diol, propane-1,3-diol, butane-1,4-diol,butane-1,3-diol, butane- 1,2-diol, pentane-1,5-diol, hexanediol,decanediol, diethylene glycol, triethylene glycol, tetraethylene glycolor cycloaliphatic dihydric alcohols of 5 to 12 carbon atoms, e.g.cyclohexane-1,1-diol, cyclohexane-1,2-diol, cyclohexane-1,3-diol,cyclohexane-1,4-diol, cyclohexanedimethanol ortricyclododecanedimethanol with diisocyanates of which the isocyanategroups are bonded to linear or branched aliphatic, cycloaliphatic oraromatic radicals of 6 to 15 carbon atoms, e.g. hexamethylenediisocyanate, 2,2,5-trimethylhexamethylene diisocyanate, toluylenediisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate ordicyclohexylpropane diisocyanate, using a ratio of about 1 OH equivalentto 2 NCO equivalents, reacting the remaining isocyanate groups with from10 to 90 equivalent percent of the hydroxyl groups of a polyol having amolecular weight of up to about 2,000, preferably <500, and reacting theremaining hydroxyl groups of this reaction product to the extent of from10 to 100% with vinyl isocyanate.

Suitable polyols having a molecular weight of up to about 2,000,preferably <500, with which the reaction product of the hydroxyalkylacrylate or hydroxyalkyl methacrylate and diisocyanate is reacted, arepolyhydric alcohols, polyether-ols and polyester-ols with at least two,preferably from 3 to 6, free hydroxyl groups. Examples of suitablepolyhydric alcohols are ethylene glycol, diethylene glycol, triethyleneglycol, tetraethylene glycol, propylene glycol, dipropylene glycol,butane-1,2-diol, butane-1,3-diol or butane-1,4-diol, pentane-1,5-diol,neopentyl-glycol, trimethylolpropane, pentaerythritol,dipentaerythritol, mannitol, sorbitol and other hexitols, preferablytrimethylolpropane, pentaerythritol and the neopentylglycol ester ofhydroxypivalic acid. Examples of suitable polyether-ols areoxyethylation products or oxypropylation products of ethylene glycol,propylene glycol, trimethylolpropane, pentaerythritol, mannitol andsorbitol, and polytetrahydrofuran.

Examples of suitable polyester-ols are condensation products of adipicacid and ethylene glycol, adipic acid, ethylene glycol andbutane-1,4-diol, adipic acid, phthalic acid, trimethylolpropane andpropylene glycol, phthalic acid and trimethylolpropane, and phthalicacid and pentaerythritol.

Mixtures of the above compounds may also be used as the polyol. Thereaction of the hydroxyalkyl acrylate or methacrylate with diisocyanateis carried out, as is the reaction of the resulting product with thepolyol, in accordance with the conventional methods for the reaction ofOH groups with isocyanate groups, such as are to be found, for example,in the book by Houben-Weyl, Methoden der organischen Chemie, VolumeXIV/2, pages 57 et seq. (1963), advantageously in the presence ofsolvents and catalysts, at from 20° to 80° C.

The reaction of the reaction product of the hydroxyalkyl acrylate ormethacrylate, diisocyanate and polyol with vinyl isocyanate isadvantageously carried out in the presence of a catalyst and of asolvent or of a copolymerizable monomer, at from 20° to 100° C.

Particularly advantageous examples of olefinically unsaturated compounds(A) which contain urethane groups are reaction products of about 130parts of hydroxypropyl acrylate or hydroxyethyl methacrylate with about174 parts of toluylene diisocyanate or about 222 parts of isophoronediisocyanate, which are then reacted with from 378 to 3,400 parts of asaturated polyester obtained from adipic acid, phthalic acid,trimethylolpropane and propylene glycol (OH number 165 mg of KOH/g) orwith from 157 to 1,433 parts of a branched polyether obtained fromtrimethylolpropane and propylene oxide (OH number 390 mg of KOH/g), andare finally reacted with from 7 to 621 parts of vinyl isocyanate.

The component (A) can be used as the sole binder. To achieve specialeffects, e.g. properties suitable for a specific use, it is in manycases advantageous to combine the vinylurethane with component (B).

(B) Suitable olefinically unsaturated compounds (B) copolymerizable withcomponent (A) are, in particular, those which have a boiling point ofabove 50° C., preferably above 100° C. Lower-boiling compounds are ingeneral less suitable, since they evaporate too easily after applicationof the coating composition, but before the latter has cured. This canalter the analysis of the coating composition and also lead to pollutionof the environment by malodorous and, in some cases, toxic monomers.Compounds having a vapor pressure of less than about 10 mm Hg at 100° C.are therefore particularly preferred for finishes and printing inkswhich do not pollute the environment.

The molecular weight of component B can vary within wide limits from 70to 20,000, i.e. both low molecular weight and high molecular weightcompounds may be employed. Examples of suitable components B are:

1. Esters of unsaturated monocarboxylic acids or dicarboxylic acids,e.g. esters of acrylic acid, methacrylic acid, α-cyanoacrylic acid,crotonic acid, cinnamic acid, sorbic acid, maleic acid, fumaric acid oritaconic acid with aliphatic, cycloaliphatic or aromatic-aliphaticmonohydric to tetrahydric alcohols of 3 to 20 carbon atoms, e.g. methylacrylate and methacrylate, n-, i- and t-butyl acrylate and methacrylate,2-ethylhexyl acrylate, lauryl acrylate, dihydroxydicyclopentadienylacrylate and methacrylate, methylglycol acrylate, hydroxyethyl acrylateand methacrylate, hydroxypropyl acrylate and methacrylate, ethyleneglycol diacrylate, diethyl glycol diacrylate, triethylene glycoldiacrylate, neopentyl-glycol diacrylate and dimethacrylate,1,4-dimethylolcyclohexane diacrylate, pentaerythritol triacrylate,tetraacrylate, trimethacrylate and tetramethacrylate, ethylα-cyanoacrylate, ethyl crotonate, ethyl sorbate, diethyl maleate,diethyl fumarate and the diacrylate and dimethacrylate of oxyalkylatedbisphenol A.

2. Amides of acrylic acid or methacrylic acid, which may or may not besubstituted by alkyl, alkoxyalkyl or hydroxyalkyl at the nitrogen, e.g.N,N'-dimethylacrylamide, N-isobutylacrylamide, diacetone-acrylamide,N-methylolacrylamide, N-methoxymethylacrylamide,N-butoxymethylacrylamide, N-butoxymethylmethacrylamide and ethyleneglycol bis-(N-methylolacrylamide) ether.

3. Vinyl esters of monocarboxylic acids or dicarboxylic acids of 2 to 20carbon atoms, e.g. vinyl acetate, vinyl propionate, vinyl2-ethylhexanoate, vinyl versatate, divinyl adipate and the like.

4. Vinyl ethers of monohydric or dihydric alcohols of 3 to 20 carbonatoms, e.g. isobutyl vinyl ether, hexyl vinyl ether, octadecyl vinylether, ethylene glycol divinyl ether, diethylene glycol divinyl ether,butanediol divinyl ether and hexanediol divinyl ether.

5. Mono-N-vinyl compounds, e.g N-vinylpyrrolidone, N-vinylpiperidone,N-vinylcaprolactam, N-vinylmorpholinone, N-vinyloxazolidone,N-vinylsuccinimide, N-methyl-N-vinylformamide, N-vinylcarbazole anddivinylureas.

6Styrene and its derivatives, e.g. α-methylstyrene, 4-chlorostyrene and1,4-divinylbenzene.

7. Allyl ethers and allyl esters, e.g. trimethylolpropane diallyl ether,trimethylolpropane triallyl ether, pentaerythritol triallyl ether,diallyl maleate, diallyl fumarate and diallyl phthalate.

8. Unsaturated polyesters having a molecular weight of from 500 to 5,000and containing from 0.5 to 10 double bonds per 1,000 molecular weightunits, the polyesters being manufactured from, for example,

(a) from 10 to 70 percent by weight of α,β-unsaturated dicarboxylicacids, e.g. maleic acid, fumaric acid or itaconic acid,

(b) from 0 to 60 percent by weight of saturated aliphatic,cycloaliphatic or aromatic dicarboxylic acids, e.g succinic acid, adipicacid, tetrahydrophthalic acid, hexahydrophthalic acid,cyclohexane-1,4-dicarboxylic acid, phthalic acid, isophthalic acid orterephthalic acid,

(c) from 20 to 80 percent by weight of aliphatic, cycloaliphatic ornon-phenolic aromatic diols, e.g. ethylene glycol, diethylene glycol,triethylene glycol, propane-1,2-diol, propane-1,3-diol, butane-1,2-diol,butane-1,3-diol, butane-1,4-diol, but-2-ene-1,4-diol, neopentyl-glycol,hexane-1,6-diol or oxyalkylated bisphenol A,

(d) from 0 to 5 percent by weight of tricarboxylic acids ortetracarboxylic acids, e.g. trimellitic acid, pyromellitic acid orbenzenetetracarboxylic acid,

(e) from 0 to 10 percent by weight of monocarboxylic acids, e.g. aceticacid, propionic acid or benzoic acid,

(f) from 0 to 5 percent by weight of trifunctional or tetrafunctionalalcohols, e.g. glycerol, trimethylolpropane or pentaerythritol, and

(g) from 0 to 10 percent by weight of monofunctional alcohols, e.g.methanol, ethanol, propanol or butanol.

9. Unsaturated epoxy resins which have been manufactured from, forexample,

(a) monofunctional epoxides and acrylic acid or methacrylic acid, asdescribed in U.S. Pat. No. 2,484,487,

(b) bifunctional epoxides and unsaturated fatty acids, as described inU.S. Pat. No. 2,456,408,

(c) polyfunctional aromatic epoxides and crotonic acid, as described inU.S. Pat. No. 2,575,440 or

(d) polyfunctional aromatic or aliphatic glycidyl ethers and acrylicacid and methacrylic acid, as described in U.S. Pat. No. 2,824,851.

10. Unsaturated polyurethanes obtained from hydroxyalkyl acrylates anddiisocyanates, with or without polyols or polyamines, for examplesaturated unsaturated polyester-polyols, polyether-polyols orcopolymer-polyols, as are described, for example, in German Laid-OpenApplication DOS No. 1,644,797 or, for printing ink purposes, in GermanLaid-Open Application DOS No. 2,358,948.

11. Unsaturated copolymers, for example manufactured by reacting

(a) copolymers, containing maleic anhydride groups, with unsaturatedalcohols, for example as described in German Laid-Open Application DOSNo. 2,050,893 or

(b) acrylic ester copolymers or polyesters, containing carboxylic acidgroups, with olefinically unsaturated epoxides, e.g. glycidyl acrylate.

12. Butadiene polymers in which the double bonds are predominantlypresent as vinyl side groups.

13. Diallyl phthalate prepolymers.

14. Poly-N-vinylurethanes, manufactured, for example, as described inGerman Laid-Open Application DOS No. 2,064,701 by reacting vinylisocyanate with saturated or unsaturated polyester-polyols,polyether-polyols or polyfunctional alcohols.

Mixtures of the various unsaturated compounds (B) can of course also beused.

Particularly preferred components (B) are acrylic monomers and N-vinylmonomers, unsaturated polyesters and epoxide-acrylates. Component (A)can be combined with up to 95, preferably with up to 70, percent byweight of component (B).

The coating composition of the invention may, depending on its intendeduse, also contain the relevant additives, for example:

1. from 0 to 70, preferably from 10 to 50, percent by weight ofinorganic or organic pigments, e.g. carbon black, titanium dioxide,chalk, baryte, zinc white, lithopone, chromium yellow, yellow iron oxideor complex pigments, e.g. phthalocyanines, azo pigments, anthraquinonecolorants and quinacridone pigments.

2. From 0 to 10, preferably from 0.001 to 3, percent by weight of dyes,e.g. eosin, crystal violet or malachite green.

3. From 0 to 10, preferably from 1 to 5, percent by weight of levelingagent, e.g. butyl acetate, butanol and silicones.

4. From 0 to 1, preferably from 0.001 to 0.5, percent by weight ofinhibitors.

5. From 0 to 70, preferably from 10 to 50, percent by weight of fillers.

6. From 0 to 10, preferably from 1 to 5, percent by weight of diluents.

7. From 0 to 70, preferably from 10 to 50, percent by weight of inertsynthetic resins, e.g. aminoplasts, alkyd resins or styrene/acrylatecopolymers.

8. From 0 to 7, preferably from 0.5 to 5, percent by weight of waxes.

9. From 0 to 5, preferably from 0.2 to 5, percent by weight ofthixotropic agents.

The coating compositions of the invention are cured by copolymerizationof components A and B. This may be effected thermally, by directheating, by means of infrared radiation or with the aid of initiators,but preferably by using high energy radiation.

For the thermal polymerization, temperatures of from 20° to 200° C. areemployed; the conventional initiators, e.g. organic peroxides or azocompounds, and accelerators, e.g. cobalt salts, may be added in amountsof from 0.5 to 6 percent by weight.

Radiation curing may be effected with UV rays or by electron beams. Inthe former case, conventional photoinitiators, such as are described,for example, by B. J. Kosar in "Light Sensitive Systems", Wiley, 1965,pages 158-193, are added. Preferably, the following are used: Benzoin,benzoin ethers, diacetyl, benzil, benzil monoketals, benzophenone,Michler's ketone, xanthones, anthraquinones, sulfur compounds, e.g.disulfides, thiols and dithiocarbamates, and carbonyl compounds. e.g.triphenylphosphine-iron tetracarbonyl in conjunction with chlorinedonors, each in amounts of from 1 to 3 percent by weight. Details of themethod of curing by UV radiation are to be found in"Photopolymerization" by H. Barzynski, K. Penzien and O. Volkert inChemiker-Zeitung 96 (1972), 545-551, and in German Laid-Open ApplicationDOS No. 2,251,933. Electron beam curing is described in detail in GermanLaid-Open Application DOS No. 2,049,715 cited above, in which furtherdetails regarding advantageous coating thickness, radiation doses andirradiation times may also be found.

The coating compositions of the invention may be used for the productionof coatings and finishes on metals, wood, plastic, leather and paper.These coatings may be used as protective layers or for decorativepurposes.

The coating compositions may also be used as a photopolymer layer forprint carriers, e.g. relief print plates or planographic print plates,or for photoresists. In such cases, they are cured by image-wiseirradiation of the coated carrier; no curing occurs in the unexposedzones and these parts of the layer are dissolved out again.

Finally, the coating compositions may also be used for the manufactureof UV-curing printing inks and print pastes. Using such inks and pastes,substrates, e.g. paper, metals or plastic films, are printed with thepigment-containing binders in order to apply a layer from about 0.5 to 5μm thick. The binders cure very rapidly on ultaviolet irradiation andthe ink becomes fixed to the substrate. The printing inks manufacturedusing the coating compositions of the invention are distinguished byextremely rapid drying even if only 1 or 2 ultraviolet lamps are used inthe case of four-color printing, and by very high printing speeds. Thedrying prints have very good scuff resistance. This resistance is muchimproved over conventional ultraviolet printing inks in the case ofcolors which are, from this point of view, particularly critical inultraviolet printing, e.g. blue and black. These remarks applyparticularly to prints produced at maximum print speeds and hence withminimum irradiation times.

If no pigments are added, the binders may be used as over-printingvarnishes.

It is particularly advantageous to use the coating compositionsaccording to the invention for printing inks and overprinting finishes.

In the Examples, parts and percentages are by weight.

EXAMPLE 1

148 parts of butanediol monoacrylate are dissolved in 200 parts of ethylacetate. 0.08 part of dibutyl-tin dilaurate is added and 69 parts ofvinyl isocyanate are then added dropwise at from 50° to 60° C., whilststirring. The reaction is then allowed to continue for from 1 to 2hours, until the isocyanate content has fallen to below 0.1%. 0.2 partof hydroquinone methyl ether is then added and the solvent is strippedoff under reduced pressure. A pale greenish yellow liquid is obtained invirtually quantitative yield.

A solution is prepared from the following components: 64 parts of anadduct of 2 moles of acrylic acid with 1 mole of bisphenol A diglycidylether (double bond vlue 0.38 equivalent/100 g), 16 parts ofbutane-1,4-diol diacrylate and 20 parts of the above reaction product.

This solution is knife-coated as a layer 60 μm thick onto surface-filledchipboard and is cured with 320 KV electrons at a belt speed of 80m/minute, corresponding to a radiation dose of 0.875 Mrad. Ascratch-resistant, tack-free coating of great hardness (Konig pendulumhardness 200 seconds) is obtained.

EXAMPLE 2

A reaction product of technical-grade butane-1,4-diol diglycidyl ether(epoxide equivalent weight 151) and the equivalent amount of acrylicacid is reacted with the equivalent amount of vinyl isocyanate asdescribed in Example 1 to give the corresponding vinylurethane, which isapplied onto paper as a layer 20 μm thick, and is cured. A tack-free,very glossy coating is obtained.

EXAMPLE 3

130 parts of hydroxypropyl acrylate are added dropwise to a solution of174 parts of toluylene diisocyanate in 400 parts of ethyl acetate in astirred vessel at from 50° to 60° C. As soon as the isocyanate value ofthe mixture has fallen to 5.9-6.0%, 680 parts of a polyester obtainedfrom adipic acid, phthalic acid, trimethylolpropane and propane glycol(OH number 165 mg of KOH/g) are run in and 0.5 part of dibutyl-tindilaurate is added. During the addition and the subsequent reaction thetemperature is kept at from 50° to 60° C. When the isocyanate value hasfallen to below 0.1%, 69 parts of vinyl isocyanate are added dropwise,again at from 50° to 60° C., and the batch is allowed to contnue toreact at this temperature until the isocyanate value has again fallen tobelow 0.1%. 1.1 parts of hydroquinone monomethyl ether are then added.

The solvent is removed from the reaction product under reduced pressure.The solvent-free resin is diluted with a mixture of equal parts oftrimethylolpropane triacrylate and ethyldiglycol acrylate. The resinsolution has the following composition: 50% of acrylic-vinylurethane,25% of trimethylolpropane triacrylate and 25% of ethyldiglycol acrylate.

60 μm thick layers are coated onto blackplate by means of a filmspreader and are cured with 320 KV electrons at a belt speed of 70m/min, corresponding to a radiation dose of 1 Mrad. The cured coatingfilm adheres well to the substrate and is tack-free andscratch-resistant.

COMPARATIVE EXAMPLE

340 parts of a polyester obtained from adipic acid, phthalic acid,trimethylolpropane and propylene glycol (OH number 165 mg of KOH/g) aredissolved in 200 g of ethyl acetate in a stirred vessel at from 50° to60° C., and 0.25 part of dibutyl-tin dilaurate is added. 69 parts ofvinyl isocyanate are added dropwise whilst keeping the temperatureconstant and the reaction is allowed to continue until the isocyanatevalue has fallen to below 0.1%. 0.4 part of hydroquinone monomethylether is added and the solvent is removed under reduced pressure.

The solvent-free resin is dissolved in a mixture of equal parts oftrimethylolpropane triacrylate and ethyldiglycol acrylate. The solutionhas the following composition:

50% of vinylurethane, 25% of trimethylolpropane triacrylate and 25% ofethyldiglycol acrylate.

A 60 μm thick layer of the resin solution is coated onto black-plate bymeans of a film spreader and is cured with 320 KV electrons at a beltspeed of 40 or 70 m/min, corresponding respectively to a dose of 1.75 or1.0 Mrad. The film cured with 1.75 Mrad is tack-free andscratch-resistant, whilst the film cured with 1.0 Mrad is notscratch-resistant and is slightly tacky.

We claim:
 1. A radiation-curable binder for coating compositions whichbinder comprises one or more olefinically unsaturated compounds of thegeneral formula (I) ##STR4## where x and y may be identical or differentand each is a number from 1 to 5, R is hydrogen or methyl, R' is adivalent linear or branched radical of 2 to 16 carbon atoms which may ormay not contain oxa groups, or is a divalent cycloaliphatic radical of 5to 12 carbon atoms, R" is a divalent linear or branched aliphatic,cycloaliphatic or aromatic radical of 6 to 15 carbon atoms and R'" is aradical which is derived from a polyhydric alcohol, a polyether-ol or apolyester-ol and which has a valency corresponding to the sum of x+y,with or without additional other radiation-curable olefinicallyunsaturated compounds having acrylyl radicals.
 2. The binder of claim 1,wherein R'" is derived from a polyester-ol.
 3. The binder of claim 1,wherein R'" is derived from a polyether-ol.
 4. The binder of claim 1,wherein R'" is derived from a polyhydric alcohol.
 5. The binder of claim2, 3 or 4, wherein said additional other radiation-curable olefinicallyunsaturated compounds have molecular weights of from 70 to 20,000 andboiling points above 50° C.
 6. The binder of claim 2, 3 or 4, whereinsaid additional other radiation-curable olefinically unsaturatedcompounds are one or more materials selected from the group consistingof esters of unsaturated monocarboxylic or dicarboxylic acids withaliphatic, cycloaliphatic or aromatic-aliphatic monohydric totetrahydric alcohols of 3 to 20 carbon atoms, amides of acrylic acid ormethacrylic acid, which may or may not be substituted by alkyl,alkoxyalkyl or hydroxyalkyl at the nitrogen, unsaturated polyestershaving a molecular weight of from 500 to 5,000 and containing from 0.5to 10 double bonds per 1,000 molecular weight units, unsaturated epoxyresins, unsaturated polyurethanes obtained from hydroxyalkyl acrylates,diisocyanates and polyols or polyamines, reaction products orcopolymers, containing maleic anhydride groups, with unsaturatedalcohols, and reaction products of acrylic ester copolymers orpolyesters containing carboxylic acid groups, with olefinicallyunsaturated epoxides.
 7. The binder of claim 2, which is the reactionproduct of vinyl isocyanate with a compound selected from the groupconsisting of hydroxypropyl acrylate, hydroxybutyl acrylate,hydroxyethyl acrylate and the adduct of 2 moles of acrylic acid with 1mole of butanediol diglycidyl ether.
 8. The binder of claim 5, whereinthe total composition contains up to 95% by weight of said additionalother radiation-curable olefinically unsaturated compounds.
 9. Thebinder of claim 5, wherein the total composition contains up to 70% byweight of said additional other radiation-curable olefinicallyunsaturated compounds.